The invention relates to heat exchangers, for motor vehicles in particular.
It relates more particularly to a heat exchanger suitable for constituting either a radiator for cooling the engine, or a radiator for heating the passenger compartment, or even an evaporator or a condenser of an air-conditioning circuit.
A heat exchanger of this type generally comprises a bank of tubes mounted between two fluid chambers by way of respective manifolds, and is suitable for being traversed by a fluid. In the case of a radiator for cooling the engine or of a radiator for heating the passenger compartment, this fluid is the liquid serving for the cooling of the engine. In the case of an evaporator or of an air-conditioning condenser, this fluid is a refrigerant fluid.
The fluid is generally distributed among the tubes of the bank by successive passes in different groups of tubes and in given respective directions of circulation.
The bank usually comprises either flat tubes combined with spacers of corrugated shape, or tubes with a circular or oval cross-section passing through a series of fins. In this case, the change of pass is obtained by virtue of transverse and longitudinal partitions situated within the fluid chambers which are provided at the two ends of the bank of tubes.
These partitions are either affixed and brazed between the fluid chamber and the corresponding manifold, or obtained by stamping of the fluid chamber so as to define compartments which communicate respectively with groups of tubes of the bank.
In this known technique, the manifold includes apertures, also called slots, equipped with rising collars into which the extremities of the tubes are inserted and brazed.
This results in the necessity for the longitudinal partitions of the fluid chambers to be notched in order to fit perfectly with the shapes of the manifold.
Hence, in the prior art, the problem is always posed of obtaining perfect leaktightness between the manifold, the longitudinal partition of the fluid chamber and the tubes.
The object of the invention is especially to surmount the abovementioned drawbacks.
To that end the invention proposes a heat exchanger of the type defined in the introduction, in which the tubes each include several channels separated by at least one longitudinal partition and are arranged along a single row, parallel to two large faces of the exchanger. In this heat exchanger, the circulation of the fluid takes place in at least two layers parallel to the large faces of the exchanger and each formed by some of the channels of the tubes, and at least one of the fluid chambers comprises an internal longitudinal partition suitable for dividing the fluid chamber into at least two longitudinal compartments communicating respectively with the two layers.
Thus the heat exchanger of the invention comprises tubes each having several channels, the respective channels of each tube being divided in each case into at least two groups corresponding to circulation layers.
In the particular case of an exchanger with two circulation layers, each situated close to one of the large faces of the heat exchanger, each tube is divided into two groups, a first group which corresponds to a first layer and a second group which corresponds to a second layer.
These two layers thus communicate respectively with the two longitudinal compartments defined in at least one of the two fluid chambers.
A tube according to the invention includes at least two channels which then correspond respectively with the two abovementioned longitudinal compartments. In the case in which each tube includes more than two channels, the numbers of channels in the first group and in the second group may be equal or different.
According to another characteristic of the invention, at least one of the fluid chambers comprises at least one transverse partition suitable for dividing the fluid chamber into at least two transverse compartments at least one of which establishes a communication between two layers.
According to yet another characteristic of the invention, each layer is divided into at least two sub-layers linked in series and in which the circulation of the fluid takes place in counter-current mode from one sub-layer to the next one.
Hence, in a typical embodiment, the heat exchanger comprises two layers, each divided into two sub-layers, which makes it possible to define a circulation with four passes: two successive passes in the two sub-layers of a first layer, and then two successive passes in the two sub-layers of a second layer.
In one preferred embodiment of the invention, each manifold includes apertures, also called slots, surrounded by collars for the insertion of the extremities of the tubes of the bank, and provision is made for each manifold to be equipped with a flat surface for brazing of a fluid chamber.
This characteristic is particularly advantageous since it makes it possible to oppose a perfectly flat surface in order to position the longitudinal partition and/or the transverse partition of the fluid chamber.
To that end, provision is made for each fluid chamber to comprise a flat contour and at least one co-planar partition (longitudinal partition and/or transverse partition) suitable for being brazed against the surface of the manifold.
It can be envisaged producing the flat surface in a single piece with the manifold.
However, in one preferred embodiment of the invention, the flat surface of each manifold forms part of a manifold plate affixed by brazing onto the manifold and including apertures aligned with the apertures of the manifold.
This makes it possible to produce a flat, reference surface from a plate including apertures, advantageously obtained by punching.
The heat exchanger of the invention may comprise at least one lug originating from one edge of the manifold or from the manifold plate, or from the fluid chamber, the said lug being folded respectively onto one edge of the fluid chamber, or onto one edge of the manifold or of the manifold plate.
According to another characteristic of the invention, the extremity of at least one longitudinal partition of the tube is positioned substantially at the level of the flat surface of the manifold, in such a way that this longitudinal partition of the tube can be brazed onto an internal longitudinal partition of the fluid chamber.
The fluid chambers are advantageously each formed by stamping of a metal plate in order to define the flat contour and the co-planar partition.
Hence, when a fluid chamber is brazed against the corresponding flat surface, the contour of the fluid chamber and the partition or partitions thereof are brazed closely against the flat surface, which makes it possible to delimit compartments communicating with the tubes in an appropriate way for defining a circulation in several passes.
According to another advantageous characteristic of the invention, at least one of the fluid chambers comprises at least one inlet or outlet pipe for fluid.
The tubes of the heat exchanger of the invention are capable of numerous embodiment variants. Hence, provision may be made, for example, for each tube to be an extruded tube, or for each tube to be formed from sheet metal folded and closed by longitudinal brazed joints, or else for each tube to be formed from two stamped sheet metal plates which are brazed together so as to be leaktight.
According to yet another advantageous characteristic of the invention, the channels of the tubes are separated by partitions the respective thicknesses of which decrease from a central region of the tube towards the periphery.
In one preferred application of the invention, the heat exchanger constitutes an evaporator for an air-conditioning apparatus.